Heretofore, various transportable or portable heaters for use in outdoor environments or the like, such as a gas stove and a hand warmer, have been widely prevalent. These conventional heaters have involved such inconveniences that only a local region of a user's body can be warmed or a level of warmth cannot be controlled. There has also been commercialized one type of portable heater using a battery and incorporating an electrical resistive element distributedly arranged therein to generate heat based on electrical energy from the battery, such as a heating garment and a heating mat. In this type of portable heater, the battery has been apt to fail to supply required heating energy for a sufficient time of period, because a mass/energy density of the battery is not so high even today.
For solution of the above problems, there has been known a garment comprising carrying out catalytic combustion of liquefied petroleum gas (LPG) as an energy source to produce heat which is transferred by means of air convection to warm up a user's body (see, for example, the following Patent Publication 2). In view of difficulty in transferring heat to every corner only by means of air convection, there has also been known a heating apparatus comprising a thermoelectric conversion element installed in a burner, such as a catalytic burner, and a heat-transfer-medium circulation device adapted to be driven by an electromotive force of the thermoelectric conversion element (see, for example, the following Patent Publication 3).
The inventor of the present invention has also previously proposed a portable heat transfer apparatus comprising a heat drive pump incorporated in a catalytic burner and adapted to circulate heated liquid (see the following Patent Publication 1).
A catalytic combustion process in the burner mainly employed in the apparatus disclosed in the above Publication has a characteristic that a combustion reaction can be induced and maintained at a lower temperature than that in flaming combustion, without interruption due to influences of wind and slight fluctuation in an air-fuel ratio. In reality, there exists a problem that, if the reaction is continued at a stoichiometrical air-fuel ratio for a relatively long period of time, a combustion temperature will be increased up to an excessive level for a catalyst, to cause a gradual deterioration in the catalyst.
In order to avoid the above problem, the reaction is performed at a air-fuel ratio set by excluding the stoichiometric air-fuel ratio. However, in cases where the air-fuel ratio is set in a direction for allowing fuel to become richer, imperfect combustion occurs to cause wasteful consumption of fuel and emission of foul-smelling exhaust gas, although ignitability can be improved to provide enhanced operational performance. In cases where the air-fuel ratio is set in a direction for allowing fuel to become leaner, although perfect combustion can be produced to eliminate wasteful consumption of fuel and emit clean exhaust gas, there is a limit to cover an air amount to be increased relative to a decrease in fuel, by an air suction function based on a non-powerful venturi tube. In particular, it is necessary for a catalyst to ensure a relatively large contact area with an air-fuel mixture, causing an increase in flow resistance. Thus, it is required to provide means for generating an extra force in addition to a gas injection force, for example, means operable to rotate a fan using an external power source (e.g., battery) to introduce air. Consequently, an apparatus to be designed as a portable type is liable to become complicated and large-scaled.
[Patent Publication 1] Japanese Patent No. 3088127
[Patent Publication 2] JP 09-126423A
[Patent Publication 2] JP 2001-116265A